EMC Made Simple®

Printed Circuit Board and System Design

 

Author:  Mark I. Montrose

Publisher:  Montrose Compliance Services, Inc.

 

Reviewed by Elya Joffe

Past President-IEEE EMC Society

Past President-IEEE Product Safety Engineering Society

 

This fifth book authored by Mark Montrose, an EMC or electromagnetic compatibility consultant and expert who self-published this incredible book is sure to be a best seller.  EMC Made Simple-Printed Circuit Board and System Design uses a totally unique style of presentation along with visual concepts to simplify both theory and application of electromagnetic compatibility.  This is especially true for those who do not work in the field of EMC on a full time basis. 

I saw an endorsement by Keith Armstrong about the book.  He said “People who communicate about EMC are experts in some way or another, and they mostly write for other EMC experts.  When they try to communicate EMC to electronic designers, most of them fail to ‘connect’.  But not Mark Montrose–whose new book “EMC Made Simple®” lives up to its title and should be on every designer’s desk”!  I fully agree with what Keith said.

Although electromagnetic theory is well known in the engineering community, many authors attempt to describe field propagation and engineering design solely using Maxwell’s equations at an academic level with a focus on mathematical analysis.  These authors usually ignore the general engineering population who has minimal exposure to the field or are at a junior or entry level.  What Mark recognized as a consultant and trainer was that missing from the bookshelf was a book that focused on the need to simplify the field of electromagnetics.  This is especially true for non-EMC engineers or those who never took a class in electromagnetics.  His approach was to not preach to the [EMC] choir, but to educate everyone on what EMC is all about.  There are few books worldwide that focus on applied engineering in a simplified, easy to read style.  Every item is discussed and fully justified with sound theory and physics. 

A most fascinating thing I read was in the Prefix.  Mark clearly identifies the target audience, or those that would benefit greatly.  He then says this book is “unsuited” for those engineers who already believe they know everything there is about EMC.  I definitely agree with his target audience!

The basic concept regarding EMC Made Simple® is understanding transmission line theory in the time domain.  Mark clearly shows that when he has an EMI problem he solves it using an oscilloscope and not a spectrum analyzer.  A spectrum analyzer only tells us the presence of an electromagnetic field, not what caused the field to be created.  An EM field is created when there is signal loss in a transmission line which is easily measured with an oscilloscope or through computational analysis.  He illustrates that it is easier to solve problems in the time instead of frequency domain for most engineers.

We propagate an electromagnetic field, usually a signal with a digital looking type of waveform from transmitter to receiver through a transmission line which is either free space or a wire.  If there is any signal loss the magnitude of this loss is the magnitude of common-mode current that gets created.  This is Kirchhoff’s law in action, yet we rarely think about Kirchhoff.  This is because our focus is almost exclusively on Ampere’s law that deals with current.   What about voltage?  Any lost propagated electromagnetic field power must travel somehow through a third wire or parasitic transmission line to satisfy Kirchhoff from receiver to transmitter.  This never before published concept is extremely elegant.   Kirchhoff is not mentioned by Maxwell yet this law is what causes job security for those working in the field of compliance.

The book is divided into six chapters, each with a focus on a particular aspect of PCB and system level design.  Each chapter has “Made Simple” in the title.

Chapter 1 is the most exciting section titled “EMC or Maxwell Made Simple®”.   Mark explains electromagnetics in a manner that has never been presented in any other book that I am aware of, with a unique twist.  He walks the reader through field theory using a visual approach as a teaching tool by converting the calculus of Maxwell into simplified algebra.  Too much emphasis is placed, in academic environments, on solving equations with no relationship to applied engineering.  What engineers need to understand is “What does Maxwell’s equations tell us, not how to manipulate mathematical formulas”.  He figured out a way to explain what each equation represents using a simplified single sentence.   Mark also explains, for the first time again in any known book, how common-mode current is actually created, not just the well know fact that common-mode current flows in a return path in the same direction as the signal path.  What caused the arrow to flip from differential-mode to common-mode?  This visualization is so unique that I am surprised that nobody has figured out by now how to explain common-mode development in a simplified manner.

Chapter 2 is the smallest chapter of the book.  “Inductance Made Simple” is an elegant discussion on what inductance is without heavy math.  It highlights the fact that every transmission line contains inductance and inductance is a significant contributor to the creation of common-mode current.  To be a successful designer, one must minimize inductance during layout.  Computational analysis or simulation can then occur after initial layout to determine if there is too much inductance and the magnitude of any signal integrity problem it may create.  

Chapter 3 is titled “Transmission Line Theory Made Simple”.  The field of electrical engineering involves sending an electromagnetic field from a source to receiver using a transmission line.  Mark explains in detail the difference between lossy and lossless transmission lines in an simplified manner.  If there is any loss of propagated electromagnetic energy in the transmission line, the magnitude of this loss becomes undesired common-mode current.  An extensive discussion also occurs on how to minimize signal propagation losses within  printed circuit board material.

I found Chapter 4 “Power Distribution Networks Made Simple” exciting to read and one of the larger sections in the book.  He explains what a capacitive structure is in simplified terms along with various design concerns and parameters that most engineers take for granted or are forgotten by senior designers.  Almost everything associated with creating a stable power distribution network, including power and return planes is discussed.  I found the section on rules-of-thumb fascinating.  He clearly investigates many rules to determine if they are valid or not, with the correct answer of “It depends” for each rule.

Moving onto Chapter 5 “Referencing Made Simple (a.k.a Grounding)” was my favorite, having authored the book Grounds for Grounding.  Mark clearly describes that the word ground is invalid in electrical engineering without a prefix to describe exactly what is being referenced.  We must reference RF field propagation to a return or reference path, not ground or a ground plane.  Various grounding methodologies are presented as well as breaking up ground loops.  Ground loops are one cause of common-mode current generation.

Chapter 6, “Shielding, Gasketing and Filtering Made Simple” is the largest chapter.  Here Mark simplifies many related topics in one chapter.  He illustrates that a metallic shield is actually a transmission line with high impedance to a propagating field.  This is uniquely described for the first time in any book that I am aware of.  This chapter also deals mainly with system design and is a must read since printed circuit boards are installed in an enclosure where shielding, gasketing and filtering may be required.

The book concludes with several Appendixes.  This includes his famous Five Algebraic Equations that are derived from Maxwell Equation, Understanding Fourier Analysis, Using the Decibel, Conversion Tables, an extensive Glossary with unique descriptions that really clarifies word(s) instead of a typical dictionary description, plus a Reference section.

This book simplifies the theory and application of applied EMC engineering, avoiding complicated math unlike other books on EMC.  It is  easy to follow, pleasant to read and a must have on the desk.  It is based on many years of practical experience of the author with “real-world” design cases.  I found it to be an excellent reference and useful for any design engineer who has to get the job done quickly and at low cost, especially those not educated in the field of electromagnetics or electromagnetic compatibility.